Touring Sovereign Hill in Ballarat on the eve of the election, Mr Guy declared Shadow Treasurer David Davis would keep his post if the Liberal-Nationals are elected.
Mr Davis did not initially supply a total estimate for new commitments when releasing the coalition's election policy costings on Thursday.
A Liberal spokesperson later confirmed they would cost about $28 billion but stressed the budget would be roughly $10b better off in net terms under their plan.
Asked why Victorians should trust Mr Davis to run the state's economy in light of the misstep, Mr Guy remained adamant the coalition were a safe pair of hands.
"I can only say this ... our commitments that David presented yesterday add up," he told reporters on Friday.
"Victorians should have full confidence now that they've been costed by the independent parliamentary budget office. It's $27.996b in costings and the $38b that we can have in saving measures are sensible and responsible."
Mr Guy guaranteed Mr Davis would be treasurer under a government he leads but couldn't explain why he did not have the figure to hand.
Victoria's major parties left voters little more than 48 hours to crunch the numbers on their policy costings before polls close.
Labor's financial statement shows its election initiatives tally about $11.7b but at least $5.86b of those have no start date for the allocation of funding over the forward estimates to 2026/27.
Labor forecasts an improved budget surplus of $1b for the 2025/26 financial year, while the coalition is flagging a $2.1b surplus in 2024/25.
It comes as the Victorian Electoral Commission braces for a slower than usual vote count, possibly delaying results on election night.
VEC communications director Sue Lang said nearly 4.4 million Victorians were enrolled to vote and about 1.93m had already cast their ballots early, which could slow counting.
"The issue that that creates for us ... is that because we've taken so many votes in the early voting centres, where they need to be counted," she told ABC radio.
"We will have 1700 voting centres tomorrow that will be staffed to count two million votes.
"But we have 155 early voting centres who need to count two million votes. So that might actually slow the count for us on Saturday night."
The VEC is aiming to count 75 per cent of votes over the weekend, absentee votes will then be sorted to their correct districts and then counted next week.
About 600,000 postal votes have been sent out but only 270,000 returned so far ahead of Saturday's 6pm mailing deadline.
Premier Daniel Andrews broke with tradition to cast his ballot early on Thursday evening, outside his electorate alongside wife Catherine and two of his children.
"Like so many other Victorians, we've got a few things happening on Saturday so we voted early and on the way to somewhere else," he tweeted.
Mr Guy will vote in Templestowe on Saturday.
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